The Coming SSTO's.

[Byeman]

The problem is the simple calculation of the altitude compensation case hasn't been done. Then the fiction is maintained that SSTO's can't carry significant payload. How can you compare the SSTO case to the TSTO case if all you know about the payload in the SSTO case is "it's some small amount"?

The story has been told about Galileo attempting to show the defenders of Earth-centered universe the Moons of Jupiter through the telescope to support the Heliocentric view. They refused to look.

Bob Clark

The main problem is that it isn't a simple calculation and it is foolish to think that a web based calculator is going to supply an accurate answer. It is also idiotic to think that this has been overlooked. Additionally, the real fiction is thinking that one can be compared to Galileo and is even close to the neighborhood of his intelligence.


Threads like these show that the internet is the downfall of human intelligence. It provides platform to spread incorrect information and opinion. And the worse offenders infect multiple websites with their nonsense.

 

[martinbayer]

It's a matter of math. It's commonly said SSTO's need some new technology or maybe even nuclear engines to carry significant payload. In truth, the fact that the exact opposite is the case can be proven by anyone who takes the time to run the rocket equation. It's actually easy to accomplish.
For instance according to SpaceX their side boosters for the Falcon Heavy will have a 30 to 1 mass ratio. With altitude compensation the Merlin can get 340 s Isp. What does the rocket equation say the delta-v will be in that case? Note how well above this value is than the delta-v needed to reach orbit.

Good. You know the rocket equation. Now apply it both to a hypothetical SSTO AND a hypothetical TSTO with the same technology basic assumptions and mission requirements and subsequently perform cost assessments with open source tools and demonstrate which one is superior in terms of specific transportation cost for the same payload capability to low Earth orbit.

Martin

 

[RGClark]

The main problem is that it isn't a simple calculation and it is foolish to think that a web based calculator is going to supply an accurate answer. It is also idiotic to think that this has been overlooked. Additionally, the real fiction is thinking that one can be compared to Galileo and is even close to the neighborhood of his intelligence.
Threads like these show that the internet is the downfall of human intelligence. It provides platform to spread incorrect information and opinion. And the worse offenders infect multiple websites with their nonsense.

The rocket equation has always been used in a first order analysis to estimate how much a launcher can send to orbit. It is in fact the very same way the conclusion was drawn that a SSTO could not carry significant payload to orbit. That conclusion was drawn however by using low Isp engines and low mass ratio stages. Science and technology progresses. The equations should now be run using the high efficiency engines and high mass ratio stages available now.
Dr. Schilling of course acknowledges his calculator does not give an exact answer to how much a launcher can deliver to orbit. It does however give a more accurate answer than just the rocket equation alone as it takes into account the reduction in Isp at sea level and the effect of the thrust level of the engines on the payload, which the rocket equation can not include.


Bob Clark

 

[RGClark]

Good. You know the rocket equation. Now apply it both to a hypothetical SSTO AND a hypothetical TSTO with the same technology basic assumptions and mission requirements and subsequently perform cost assessments with open source tools and demonstrate which one is superior.

Martin

That is what I discussed in post #196. Nobody in this discussion however has done the calculation of the SSTO case with altitude compensation. You know it's a small amount even without doing the calculation? And if the calculation shows it's actually a large amount you know it's wrong?


Bob Clark

 

[martinbayer]

I discussed the numbers for the 311 s Isp SSTO case in post #184. For the 340 s Isp SSTO case that uses altitude compensation just change the Isp number from 311 s to 340 s. You'll see the payload goes up multiple times.
For the TSTO case, a problem again is that SpaceX has not provided the propellant and dry mass numbers for the upper stage of the Falcon 9 v 1.1. An estimate puts the propellant mass in the range of 70 metric tons (mT). But what about the dry mass? It is quite likely the upper stage won't have as good a mass ratio as the first stage because it will undergo greater acceleration as propellant is burned off. This will require it to have a stronger and therefore heavier structure. I took the dry mass as an estimate as 7 mT. You can try different propellant and dry mass combinations you feel are more accurate if you wish.
Using these numbers for the upper stage, when I changed the Isp for the first stage from 311 s to 340 s the payload for this TSTO went up less than 25%.

Good. You are making baby steps towards a TSTO. I would like to point out that about 15 seconds worth of googling would provide you with mass estimates for the Falcon upper stage that are somewhat less pessimistic than yours, for example at http://www.spacelaunchreport.com/falcon9.html or http://www.spacelaunchreport.com/falcon9v1-1.html, so you a don't have to make up your own numbers, which would in turn make your posts a little more defensible, but it's a start. Now, once you've established the new TSTO payload capability, use your best engineering judgment to estimate the cost per flight for an 'upgraded' conventional Falcon 9, and once you've done the exact same for your hypothetical SSTO (remember though to factor in that the 'upgrade' costs and associated needed amortization for the SSTO will be notably higher due to the dramatic change in the vehicle concept and the associated relocation of payload adapter, fairing, avionics etc., and don't forget to accurately account for those additional masses, which eat directly into your payload), determine the specific cost per pound of payload to low Earth orbit for both and report back with your findings. I really look forward to seeing the numbers, but please don't bother trying to evade the reckoning by continuing to yammer about how low the relative gains on the TSTO are (which is of course due to the fact that it's already a pretty optimal system ).

Martin

 

[martinbayer]

No one has yet done the calculation of how high the payload can be when you use altitude compensation on a launcher with the high mass ratio's of SpaceX, either from just plugging in to the rocket equation or using Dr. Schilling's performance calculator. The assumption is simply made that it HAS to be small without actually running the numbers.
I could say what numbers I'm getting but people would believe it more when they do the calculation themselves.

Nice try. You are making an assertion, and the onus is on you, not us, to prove it. If the numbers are indeed good, correlate them with the cost per flight for both the TSTO and a hypothetical SSTO and follow the nickname of Missouri .

Martin

 

[martinbayer]

The problem is the simple calculation of the altitude compensation case hasn't been done. Then the fiction is maintained that SSTO's can't carry significant payload. How can you compare the SSTO case to the TSTO case if all you know about the payload in the SSTO case is "it's some small amount"?

The story has been told about Galileo attempting to show the defenders of the Earth-centered universe the Moons of Jupiter through the telescope to support the Heliocentric view. They refused to look.

Oh, we'd look at it alright, if you just gave us some straight answers and an actual payload number to look at instead of just vaguely gushing how great an SSTO the Falcon 9 would make, and how stupid Elon Musk has to be for not recognizing it ...

Martin

 

[martinbayer]

That is what I discussed in post #196. Nobody in this discussion however has done the calculation of the SSTO case with altitude compensation. You know it's a small amount even without doing the calculation? And if the calculation shows it's actually a large amount you know it's wrong?

If by 'discuss' you mean vaguely droning on about percentages of hypothetical improvements, then yes, you did indeed 'discuss' it. I note though that you did however NOT go ahead and actually apply the rocket equation to both a hypothetical SSTO AND a hypothetical TSTO with the same mission requirements and technology basic assumptions, i.e. the dry mass estimates for the Falcon 9 upper stage that I had to point you to, since you were apparently either unwilling or unable to research them yourself, and subsequently perform cost assessments with open source tools to clearly demonstrate which one is superior. And since, contrary to you, I never made any claims or assertions about the potential effects of altitude compensation, I am bewildered (but then again, not too much really) why you feel you have to resort to such an outright bald faced lie. Stick with the facts, please, as hard as that may be for you.

Martin

 

[RGClark]

...
Good. You are making baby steps towards a TSTO. I would like to point out that about 15 seconds worth of googling would provide you with mass estimates for the Falcon upper stage that are somewhat less pessimistic than yours, for example at http://www.spacelaunchreport.com/falcon9.html or http://www.spacelaunchreport.com/falcon9v1-1.html, so you a don't have to make up your own numbers, which would in turn make your posts a little more defensible, but it's a start. Now, once you've established the new TSTO payload capability, use your best engineering judgment to estimate the cost per flight for an 'upgraded' conventional Falcon 9, and once you've done the exact same for your hypothetical SSTO (remember though to factor in that the 'upgrade' costs and associated needed amortization for the SSTO will be notably higher due to the dramatic change in the vehicle concept and the associated relocation of payload adapter, fairing, avionics etc., and don't forget to accurately account for those additional masses, which eat directly into your payload), determine the specific cost per pound of payload to low Earth orbit for both and report back with your findings. I really look forward to seeing the numbers, but please don't bother trying to evade the reckoning by continuing to yammer about how low the relative gains on the TSTO are (which is of course due to the fact that it's already a pretty optimal system .

I'm aware of Ed Kyle's page and I'm a big fan of his site. Keep in mind though his numbers are estimates, as he indicates by putting question marks beside them. One thing that makes me hesitate to use his numbers is that for instance he is not giving the F9 v1.1 first stage the high propellant fraction that Elon stated in that Royal Aeronautical Society video.
Then he also uses about the same propellant fraction for the upper stage as the lower stage. There are two reasons to doubt this. I mentioned that upper stages often have to undergo higher acceleration then lower stages so they usually have to be more robust structurally than lower stages. This means they won't have as high a propellant fraction. Another is that rocket stages mass ratios usually get better as you scale a rocket up. Said another way the mass ratio usually gets worse as you scale it down.

Bob Clark

 

[martinbayer]

I'm aware of Ed Kyle's page and I'm a big fan of his site. Keep in mind though his numbers are estimates, as he indicates by putting question marks beside them. One thing that makes me hesitate to use his numbers is that for instance he is not giving the F9 v1.1 first stage the high propellant fraction that Elon stated in that Royal Aeronautical Society video.
Then he also uses about the same propellant fraction for the upper stage as the lower stage. There are two reasons to doubt this. I mentioned that upper stages often have to undergo higher acceleration then lower stages so they usually have to be more robust structurally than lower stages. This means they won't have as high a propellant fraction. Another is that rocket stages mass ratios usually get better as you scale a rocket up. Said another way the mass ratio usually gets worse as you scale it down.

Certainly, his numbers are estimates, but so are yours, and if you don't mind me saying, I would trust his more than yours, since he's not out to use them to simply prove his pet system, as you are. But since you raise some valid points, here's a suggestion: Why don't you run your set of Falcon 9 numbers in that Launch Vehicle Performance Calculator you keep mentioning and see what performance you come up with? If you don't match the number quoted by SpaceX, you know you have to tweak your assumptions until you do. Have fun and let us know what you find.

Martin

 

[RGClark]

...

Oh, we'd look at it alright, if you just gave us some straight answer and an actual payload number to look at instead of just vaguely gushing how great an SSTO the Falcon 9 would make, and how stupid Elon Musk has to be for not recognizing it ...

Martin

Actually, no. No one has looked at that case where you use altitude compensation and assume Elon was correct in the high propellant fraction he gave in the Royal Aeronautical Society video.
Elon is a smart guy. But nobody has given a rocket altitude compensation yet. Usually it is taken as given we are going to use different nozzles on the different stages and the performance will be adequate. Remember for a two stage system the performance boost is not so dramatic as for the SSTO, so it's not taken as worthwhile to develop altitude compensation when TSTO performance is good enough.


Bob Clark

 

[martinbayer]

Actually, no. No one has looked at that case where you use altitude compensation and assume Elon was correct in the high propellant fraction he gave in the Royal Aeronautical Society video.
Elon is a smart guy. But nobody has given a rocket altitude compensation yet. Usually it is taken as given we are going to use different nozzles on the different stages and the performance will be adequate. Remember for a two stage system the performance boost is not so dramatic as for the SSTO, so it's not taken as worthwhile to develop altitude compensation when TSTO performance is good enough.

I guess that you don't really read my posts, since I keep telling you to show your comparative results for SSTO vs. a TSTO in terms of masses, payload capability and resulting specific transportation cost. I, like everybody else with a more than cursory understanding of launch vehicle performance, am well aware that SSTOs are inherently much more sensitive to technology parameters than TSTOs, but that's really not the point - so what? The point is to demonstrate why your super duper SSTO with fancy altitude compensation would be *QUANTITATIVELY SUPERIOR WITH RESPECT TO SPECIFIC TRANSPORTATION COST* to a TSTO using the exact same technology assumptions and sized to the exact same mission requirements - only that's what counts.

Martin

 

[Byeman]

Then he also uses about the same propellant fraction for the upper stage as the lower stage. There are two reasons to doubt this. I mentioned that upper stages often have to undergo higher acceleration then lower stages so they usually have to be more robust structurally than lower stages.

You don't have the experience or knowledge to doubt his numbers. Your point about upperstages could not be more wrong. Max axial acceleration is at booster shutdown for Delta, Atlas and Falcon.

 

[Archibald]

Stop feeding the Clark monster, he did this to sci.space.policy before coming here. It's NOT worth it. Let it go.

My point exactly. Look at this
https://www.google.fr/#hl=fr&q=%22A+kerosene-fueled+X-33%22

Or this
https://www.google.fr/?gws_rd=cr&ei=2KN2Uvf2Kcqi0QXS_ICoDQ#q=%22An+SSTO%22%22as+God+and+Robert+Heinlein+intended%22

I call this TROLLING

TROLLING

 

[RGClark]

My point exactly. Look at this
https://www.google.fr/#hl=fr&q=%22A+kerosene-fueled+X-33%22
Or this
https://www.google.fr/?gws_rd=cr&ei=2KN2Uvf2Kcqi0QXS_ICoDQ#q=%22An+SSTO%22%22as+God+and+Robert+Heinlein+intended%22
I call this TROLLING

The definition of a troll is someone who initiates a discussion purely to start an argument, whether he believes the point he's making or not. That's clearly not the case here. This discussion could be ended if someone simply did the high school level math for the rocket equation of a stage with a 340s Isp of a Falcon 9 with altitude compensation that has the propellant fraction Elon Musk claims it has. Or you don't even have to do any math, just plug in numbers in Schilling's launch performance calculator and it would do the calculation for you.
But no one has. They refuse to look in the telescope.

Bob Clark

 

[Byeman]

The definition of a troll is someone who initiates a discussion purely to start an argument, whether he believes the point he's making or not. That's clearly not the case here. This discussion could be ended if someone simply did the high school level math for the rocket equation of a stage with a 340s Isp of a Falcon 9 with altitude compensation that has the propellant fraction Elon Musk claims it has. Or you don't even have to do any math, just plug in numbers in Schilling's launch performance calculator and it would do the calculation for you.
But no one has. They refuse to look in the telescope.

You are a troll that spams. Yes, it is a case of trolling. You ignore all posts that discredit your point. You post your nonsense on dozens of websites. You have been proven wrong on many of your proposals. This is just another case of the same thing and you have the audacity of comparing yourself to Galileo. There is no need to look in the telescope because you aren't Galileo but Giovanni Schiaparelli and are seeing things that are there.

Plugging numbers in calculators prove nothing, especially when the input is wrong. The mass fraction of the stage does not equate to the mass fraction of the stage as an SSTO. That is major reason you are wrong, here and with the Titan stage too.

But as a troll, you will ignore this and continue with your flawed reasoning.

 

[Byeman]

duplicate

 

[RGClark]

The definition of a troll is someone who initiates a discussion purely to start an argument, whether he believes the point he's making or not. That's clearly not the case here. This discussion could be ended if someone simply did the high school level math for the rocket equation of a stage with a 340s Isp of a Falcon 9 with altitude compensation that has the propellant fraction Elon Musk claims it has. Or you don't even have to do any math, just plug in numbers in Schilling's launch performance calculator and it would do the calculation for you.
But no one has. They refuse to look in the telescope.

You are a troll that spams. Yes, it is a case of trolling. You ignore all posts that discredit your point. You post your nonsense on dozens of websites. You have been proven wrong on many of your proposals. This is just another case of the same thing and you have the audacity of comparing yourself to Galileo. There is no need to look in the telescope because you aren't Galileo but Giovanni Schiaparelli and are seeing things that are there.
Plugging numbers in calculators prove nothing, especially when the input is wrong. The mass fraction of the stage does not equate to the mass fraction of the stage as an SSTO. That is major reason you are wrong, here and with the Titan stage too.
But as a troll, you will ignore this and continue with your flawed reasoning.

An excuse simply not to do the calculation. The rocket equation works when it shows for low Isp engines and low mass efficiency stages that SSTO is not possible. But when you use it for high Isp engines, available now, and high efficiency stages, available now, it stops working.
We know this without even attempting it. We don't know what the number is for the payload but we know it won't work. You're refusing to look into the telescope.

Bob Clark

 

[Byeman]

An excuse simply not to do the calculation. The rocket equation works when it shows for low Isp engines and low mass efficiency stages that SSTO is not possible. But when it shows for high Isp engines, available now, and high efficiency stages, available now, it stops working.
We know this without even attempting it. We don't know what the number is for the payload but we know it won't work. You're refusing to look into the telescope.

You keep looking in a telescope and seeing things that are there and ignore the data in front of you. The "high efficiency stages" for a SSTO do not exist. They may be "high efficiency" when used as their role in multi stage vehicle but when to be used as an SSTO, many systems have to be added (fairing, avionics, power, payload adapter, etc) which reduces the mass ratio. Musk excludes the interstage when brags about the stage effciency.

You are no different than moon hoaxers. You refuse to see the real data and will continue to believe no matter what the real facts are.
The students at the east coast college should demand a refund of tuition for any class that you have taught them.

 

[RGClark]

...
You keep looking in a telescope and seeing things that are there and ignore the data in front of you. The "high efficiency stages" for a SSTO do not exist. They may be "high efficiency" when used as their role in multi stage vehicle but when to be used as an SSTO, many systems have to be added (fairing, avionics, power, payload adapter, etc) which reduces the mass ratio. Musk excludes the interstage when brags about the stage effciency.
...

And you know this without even calculating it. You know it will suddenly stop being SSTO without knowing how much it would be before adding these ancillary structures. You don't know how much is the payload case without them, and you don't know what the mass of the ancillary structures is, you just know without doing the calculation that when you add them, the vehicle will no longer be SSTO.
You know this without doing any calculation.

Bob Clark

 

[overscan (PaulMM)]

Tired of this party political broadcast on behalf of the RGClark "SSTO's are easy but inexplicably noone is building them" party. RGClark is banned from posting indefinitely.